The present invention relates to a magnetophoresis type display suited to display data which are entered into a handwriting input device, and a graphic input/output device which, by utilizing such a display, in an input mode generates an electric signal (graphic signal) indicative of coordinates of a particular entered point and, in a display mode, displays a pattern associated with a supplied graphic signal.
Recently, a magnetophoresis type display has been developed and put to practical use which displays characters, graphics and other patterns which are written into a magnetrophoretic display panel by means of an electromagnet, which has a pen configuration. This type of display, developed by The Pilot Pen Co., Ltd. (Japan), includes a pair of transparent spaced sheets which are located to face each other. The clearance between the transparent sheets is partitioned to define a great number of small cells. Each of the cells is filled with viscous white liquid which contains particles of a black magnetic material such as ferrite. When a person enters a desired pattern into a certain area of one surface of the display panel using the electromagnetic pen, the magnetic particles in those cells which are covered by that particular area are magnetically attracted by the pen toward the above-mentioned surface to render the desired pattern in black. She or he may erase the displayed pattern by moving a permanent magnet on and along the other surface of the display panel to attract the magnetic particles toward that surface. This erases black patterns over the entire display surface of the panel, thereby causing the whole display surface to turn white.
The problem with the above-described type of prior art magnetophoretic display is that what it can do in an erase mode is simply cleaning the whole display surface. Specifically, where data entered into a handwriting input device are to be displayed, it is desirable to furnish the input device with a partial erase mode in order to enhance efficient partial correction of entered data. A prior art display of the type concerned, however, is incapable of partially erasing patterns being displayed despite the desirable partial erase mode.
Meanwhile, a blackboard heretofore widely used for conference and other applications is incrasingly replaced with a large-size graphic input device which functions to transform characters, graphics and other patterns entered by hand into electric signals. Specifically, the graphic input device electromagnetically senses a particular position of a pen on the input surface of a tablet and, then, generates a graphic signal indicative of coordinates of the pen input position. This type of graphic input device is disclosed in, for example, pending U.S. patent application Ser. No. 654,803 filed Sept. 25, 1984 (now U.S. Pat. No. 4,568,799 granted Feb. 4, 1986) and assigned to the same assignee as the present application. The graphic input device comprises two perpendicular groups of conductors which are arranged in an input surface of a tablet in a grid configuration. A pen used with the device for entry of data is provided with a coil. When a person enters data using the pen, the device locates an electromagnetic coupling between the conductor groups in the input surface and the coil of the pen, generating a graphic signal representative of the coordinates of the pen input point. Such graphic signals may be stored for future reproduction or transmitted to a remote location for display.
Usually, display of data which are entered into the graphic input device is implemented by a cathode ray tube (CRT). However, since the input surface of the graphic input device and the display surface of the CRT are placed in spaced positions and since they are not equally dimensioned, it needs formidable time and labor for a person to effect addition of data, partial erasure and other partial corrections while watching patterns being displayed.
An approach to eliminate the above drawback is a graphic input/output device which includes a special screen for display which is superposed on an input surface. This kind of device transforms graphic signals into image patterns and projects the image patterns onto the screen by means of a projector. Since the image patterns appearing on the screen have the same dimensions as and occupy the same positions as the previously entered patterns, a person is allowed to effect partial corrections tracing the patterns being displayed. However, the projector scheme cannot avoid the drawback that the projector and the screen have to be located at a substantial spacing from each other and, in addition, a display with high resolution is expensive.
To eliminate the drawbacks particular to the prior art graphic input devices discussed hereinabove, the present invention uses the magnetophoresis type display, particularly its display panel, as means for displaying entered data.